RECOVERY OF INCOMPLETE TABLES UNDER FUNCTIONAL DEPENDENCIES
نویسندگان
چکیده
منابع مشابه
Functional Dependencies and Incomplete Information
Functional dependencies play an important role in relational database design. They are defined in the context of a single relation which a t all times must contain tuples with non-null entries. In this paper we examine an extension of the functional dependency interpretation t o handle null values, that is, entries in tuples that represent incomplete information in a relational database. A comp...
متن کاملAxiomatisation of Functional Dependencies in Incomplete Relations
Incomplete relations are relations which contain null values, whose meaning is \value is at present unknown". Such relations give rise to two types of functional dependency (FD). The rst type, called the strong FD (SFD), is satissed in an incomplete relation if for all possible worlds of this relation the FD is satissed in the standard way. The second type, called the weak FD (WFD), is satissed...
متن کاملFunctional Dependencies of Data Tables Over Domains with Similarity Relations
We study attribute dependencies in a setting of fuzzy logic. Our dependencies are described by formulas A ⇒ B where A and B are fuzzy sets of attributes. The meaning of A ⇒ B is that any two objects that have similar values on attributes from A have also similar values on attributes from B. Our approach generalizes classical functional dependencies from databases and also several approaches to ...
متن کاملDesign by Example for SQL Tables with Functional Dependencies
An Armstrong relation satisfies the functional dependencies (FD) implied by a given FD set and violates all other FDs. Therefore, they form an instance of the design-by-example methodology: the example relation exhibits precisely those FDs that the current design perceives as meaningful for the application domain. The existing framework of Armstrong relations only applies to total relations. We...
متن کاملA Lattice View of Functional Dependencies in Incomplete Relations
Functional Dependencies (or simply FDs) are by far the most common integrity constraint in the real world. When relations are incomplete and thus contain null values the problem of whether satisfaction is additive arises. Additivity is the property of the equivalence of the satisfaction of a set of functional dependencies (FDs), F, with the individual satisfaction of each member of F in an inco...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
ژورنال
عنوان ژورنال: Bulletin of informatics and cybernetics
سال: 1982
ISSN: 0286-522X
DOI: 10.5109/13334